Hunters who hunt with a bow and arrow under certain circumstances desire to use a broadhead type arrowhead which has a plurality of radially extending longitudinally oriented blade edges spaced around the circumference of the arrowhead. The blades of the broadhead create a wider wound in the hunted animal and therefore improve the arrows effectiveness in making a kill. It is therefore desirable to maximize the distance that the blades extend outwardly from the shaft of an arrow so as to cause a correspondingly wider wound. Furthermore, the effectiveness of a broadhead is enhanced by the number of blades which are provided, and therefore broadheads typically have at least three blades, and may have as many as six blades.
Broadheads tend to reduce the accuracy of an arrow compared to other arrowheads because transverse air movements catch the enlarged surface areas of the blade during flight and cause the arrow to appear to drift, that is, not fly directly at its intended target. Openings are provided in the sides of the blades to reduce the surface area of the blades and therefore reduce the drifting of arrows fitted with broadheads. Also several attempts have been made to construct a broadhead with blades which will be at least partially retracted in flight but which will extend further outward on impact. Such prior efforts are best shown in U.S. Pat. No. 3,138,383, U.S. Pat. No. 4,973,060, U.S. Pat. No. 4,504,063, and U.S. Pat. No. 4,998,738. These prior efforts have resulted in an arrowhead having either a plunger extending longitudinally through the arrowhead from the point or having a body portion which is adapted to slide longitudinally backward relative to the shaft of the arrow on impact. Depression of the plunger or the backward motion of the arrowhead along the shaft causes the blades to be projected from a retracted position to an extended position.
Frequently the blades of arrowheads constructed as previously described tend to at least partially extend upon release of the arrow from the bow because of the inertia of the plunger or slidable arrowhead. When the arrow is accelerated by the bow, the stationary inertia of the plunger, or of the broadhead itself as the case may be, will create a force similar to the force caused on impact of the arrow and urge the blades outwardly. Arrows also have a tendency to rotate during flight, and the centrifical force caused by the rotation of the arrow during flight may also cause the blade to extend outwardly.
Furthermore, existing expandable broadheads do not have a means for retaining the blades in their retracted position until such time as the arrow impacts on the target. Consequently, one or more of the blades may move to the extended position as a result of shaking or movement of the arrow as the hunter prepares for a shot. In such cases, the existance of the expandable broadhead may cause the hunter to loose an opportune shot at a target.
It is therefore desirable to provide a broadhead having blades which can be locked in a retracted position while the hunter prepares to shoot and during the acceleration and flight of the arrow, but will extend further outwardly upon impact with a target.